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Application Of Integrals

Question
CBSEENMA12035856

Using integration find the area of the region bounded by the parabola y2 = 4x and the circle 4x2 + 4y2 = 9.

Solution

The respective equations for the parabola and the circle are:

y2 = 4x               ............(1)4x2 + 4y2 = 9     ............(2)or  x2 + y2 =322

Equations (1) is a parabola with vertex ( 0, 0 ) which opens to the right and  equation (2) is a circle with centre (0, 0 ) and radius 32.

From equations (1) and (2), we get:

4x2 + 4 ( 4x ) = 94x2 + 16x - 9 = 04x2 + 18x - 2x- 9 = 02x ( 2x + 9 ) - 1 ( 2x + 9 ) = 0 ( 2x + 9 ) ( 2x - 1 ) = 0x = -92,  12For  x = -92,   y2 = 4 -92, which is not possible, hence x = 12Therefore, the given curves intersect at x = 12.

                   

Required area of the region bound by the two curves

= 2 012 2xdx +  2 1232 94 - x2  dx= 4 23 x32012  +  2 x2 94 - x2 + 98  sin-1 2x31232 = 831812 + 2  0 +98  sin-1 1 - 14 2  - 98  sin-1 13= 83122 + 94 π2 - 22 -  94  sin-1 13= 223 + 9π8 - 22 -94  sin-1 13